Polyamide fibers are relatively inexpensive and offer a combination of desirable qualities such as comfort, warmth and ease of manufacture into a broad range of colors, patterns and textures. As a result, polyamide fibers are widely used in a variety of household and commercial articles, including, e.g., carpets, drapery material, upholstery and clothing. Carpets made from polyamide fibers are a popular floor covering for both residential and commercial applications.
Sheath/core bi-component polyamide-containing fibers are known. U.S. Pat. No. 4,075,378 to Anton discloses sheath/core bi-component polyamide fibers containing a polyamide core and a polyamide sheath. The core polyamide is acid-dyeable while the sheath polyamide is basic-dyeable due to sulfonation. Other patents disclosing sheath/core and/or other types of bicomponent fibers include U.S. Pat. No. 5,445,884 to Hoyt et al.; U.S. Pat. No. 3,679,541 to Davis et al.; U.S. Pat. No. 3,645,819 to Fujii et al.; U.S. Pat. No. 3,616,183 to Brayford; and U.S. Pat. No. 2,989,798 to Bannerman.
Fibers that are non-round in transverse cross-section are also known. For example, U.S. Pat. Nos. 2,939,202 and 2,939,201, both to Holland, describe fibers having a trilobal cross-section.
Polyamide fibers may be dyed to produce a variety of colors suitable for use in a number of textiles, including, but not limited to, fabrics and carpets. Uniform or level dyeing of polyamide fibers has been a problem that has received much attention over the years. Combinations of specific dyes and fibers have been used in an effort to improve dyeing uniformity or levelness of a given fiber, fabric, or carpet. Although some improvements have been made, further improvements in dyeing uniformity are desired by those in the textile industry, in particular the carpet industry.
What is needed in the art is a dyed polyamide fiber, which possesses superior dyeing properties, including an improved uniformity or levelness of dyeing. What is also needed in the art is a method of making a polyamide fiber having superior dyeing uniformity or levelness.